Patent GB-477334-A (GB)
Title: Improvements relating to block signalling systems for railways and the like
IPC: B61L23/12
Filed: 1936-06-24
Abstract: 477,334. Block signalling. LASCELLES, T. S., and SYKES INTERLOCKING SIGNAL CO., Ltd., W. R. June 24, 1936, No. 17548. [Class 105] Block signalling systems having block instruments of the three-position type operated by code signals over a single line wire are arranged so that a signal must be received and aclmowledged before the next signal of the series can be transmitted. The requesting station must send a code to permit the release of the commutator device at the accepting station before the latter can transmit the "line clear " or other code, which code sets the indicator at the requesting station ; the indicator at the accepting station is set when the requesting station acknowledges the receipt of the block signal. In the form shown positive current is used for the usual bell communication and negative current for the code signalling; for example, at station A a polarized relay RA applies current to the bell BA or to the decoding apparatus SA. For a train to be sent from a station A the operator at the requesting station A, after a preliminary exchange of bell signals by means of a key KA, will operate a push PM to apply a request code to the line wire L. This code is a negative current code as the push PM also closes a contact 16 whereby a relay CA is energized so that the positive pole of battery A<1> is earthed over front contact 47 while the negative pole is applied over front contacts 54, 48, wire 53, push PM, wire 55 and front contact 56 to the line wire L. At the accepting station B this negative code operates the polarized relay RB to apply current to the decoding apparatus SB. The effect of the PM code is to close a contact 30 which picks up a relay PMR having a stick winding energized over contacts 57 of the commutator C. A buzzer ZB is sounded over a front contact 60 of the relay PMR. The operator at B so notified is now enabled, on depressing a key 26, to energize a lock 24 to release the commutator C, the circuit being from +, through a contact N of the home signal lever, wire 62, front contact 63 of relay PMR, wire 64, commutator contacts 65 (still at " line blocked "), wire 66, key 26 and winding of the lock 24. The commutator is moved to the line clear " position and thereafter the operator (at B) operates a code transmitter push CT which closes a contact 37 to energize a relay CB whereby the battery B<1> is earthed at the positive pole while the negative pole is applied to the line wire L over front contacts 69, 70, wire 68, wire 80, back contact 79 (relay PMR having dropped when the initial movement of the commutator C opened contacts 57 in the stick circuit), wire 78, back contact 77 (relay RBR having dropped when its stick circuit was opened at contact 38 by the push CT), wire 76, commutator contacts 75 (closed with the commutator at the line clear position) wire 74, code transmitting push CLC, wire 71, and front contact 51. The push CT depresses all the pushes CLC, CLB, CTL but only one of these is effective at a time. At the requesting station A this " line clear " code causes a contact 9 to close whereby relays AKR, LCR and the indicator LC are energized. The relays AKR, LCR are provided with stick windings. A front contact 87 of relav AKR causes a buzzer ZA to sound. The operator at A thereupon depresses a push ACK which opens a contact 20 to break the stick circuit of relay AKR and also causes an acknowledgment code to be sent to B. The acknowledgment code at B causes a contact 31 to close whereby the indicator LC is energized since commutator contact 92 is closed (the commutator being at the " line clear " position). To release the starting signal at A, the operator depresses a key S<4> to energize the lock magnet S<3>, the circuit being +, contact 19, wire 81, front contact 82 of stick relay ASR, wire 83, front contact 84 of the picked up relay LCR, wire 93, back contact 94 of relay AKR (dropped after acknowledgment was sent), wire 95, key S<4> and magnet S3. The entry of a train opens a treadle contact T<1> to break the stick circuit of relay ASR, a back contact 98 of which sounds the buzzer ZA until the signal lever has been put back to normal so opening the contact LR. The operator (at A) so notified of the train entry, depresses his push PM to send the PM code to B. At B this code causes the relay PMR to be energized as previously described whereby the buzzer ZB is sounded and the lock magnet 24 is able to be energized (on depressing the key 26) thereby to permit the commutator C to be set to the " train on line " position. The operator at B then operates the code transmitter CT but only the push CTL is effective, the battery line 68 being connected thereto over contacts 96 of the commutator (now set at " train on line " position). This " train on line " code effects at station A the closure of a contact 7 whereby the relay AKR, the indicator TL and a relay TLR are energized. The operator A acknowledges as before and this code at station B closes the contact 31 to energize the indicator TL over commutator contacts 97. When the train passes beyond the home signal at B a treadle contact T3 is closed whereby the relay RBR is picked up, and its front contact 105 sounds the buzzer ZB. The operator B puts the signal back to danger and sets the commutator C to the line blocked " position as the look magnet 24 can be energized from +, over the signal lever contact N, front contact 113 of the relay RBR, wire 112, commutator contacts 111 (closed while the commutator is still at the " train on line " position), wire 66, key 26 and magnet 24. After moving the commutator the operator depresses the code transmitter CT but only the push CLB is effective, the negative current being applied over wires 68, 80, back contact 79 of relay PMR, wire 78, front contact 77 of relay RBR, wire 117, commutator contacts 118, wire 119, contact 35 (closed when the indicator B<2> is at the " train on line " position), wire 120, push CLB, and so to wire 71 and the line wire L. Relay RBR is maintained energized over commutator contacts 115 in spite of the opening of the push contact 38. At station A this " line blocked " code effects the closure of a contact 8 to energize the relay AKR and the indicator LB and to pick up the relay ASR. The buzzer ZA is sounded over front contact 87 of relay AKR and accordingly the operator at A depresses the push ACK to send the acknowledgment code which at station B energizes the indicator LB over contact 31 and commutator contacts 124. A cancellation push CL at station A permits the system to be directly restored to normal after a line clear indication has been given. No train must have entered and the starting signal, must be at danger. Such being the case, negative current is applied from wire 53 over contact 125 (lock magnet S3 dropped), signal lever contact N, back contact 127 of relay LCR (dropped by the opening of contact 19 when the cancellation push CL was depressed), wire 128 front contact 129 of relay ASR (no train having entered), the push CL, and so to the wire 55 and the line wire L. At station B the cancellation code effects the closure of contact 32 whereby the relay RBR, which was dropped when " line clear was sent from B, is re-energized. The buzzer ZB is sounded over front contact 105 of relay RBR and commutator contacts 109. A reverse lock magnet 25 for the commutator can now be energized from +, over signal lever contact N, wire 62, front contact 113 of relay RBR, wire 112, commutator contacts 134, wire 135, key 27 and magnet 25. With magnet 25 energized the commutator C can be directly returned (in the counterclockwise direction) to normal. The operator at B can now operate code transmitter CT to send " line blocked " code, the negative current being applied from wires 68, 80, back contact 79 of relay PMR, front contact 77 of relay RBR, wire 117, commutator contacts 118, wire 119, contact 36 (closed with indicator B<2> at " line clear "), push CLB, and so to wire 71 and line wire L. At station A this code sets the indicator to "line blocked." The operator A acknowledges and thereby the indicator at station B is set to " line blocked " by the closure of contact 31. The code transmitting and receiving arrangements may be of the constant total code character as described in Specification 397,118, [Group XXXVIII].